life Vegetation

2000 Technical Report #4

Wil life and Vegetation Surveys ALAMAGAN 2000

Conducted By

CNMI Division of Fish and Wildlife Wildlife Section

VVith Assistance From

The Northern Island Mayor's Office

10-17 JUNE 2000

Please cite as:

Cruz.

Arriola. . Johnson. and G. Beauprez. 2000. Wildlife and

Vegetation Surveys Alamagan 2000. Technical Report #4 C MI-DFW. unpubl.

SUMMARY OF WILDLIFE SURVEYS ALAMAGAN ISLAND

10-17 JUNE 2000

Conducted by:

CNMI Division of Fish and Wildlife Wildlife and Enforcement Sections

P.O. Box 10007 Lower Base, Saipan 96950

and

Northern Islands Mayor's Office P.O. Box 502859

Garapan, Saipan 96950

Executive Summary

Alamagan is unique in having the only well established population of endangered Nightingale reed-warblers outside of Saipan. Alamagan was visited from 10-17 June 2000 to assess forest bird, fruit bat, lizard, and small mammal populations.

Bird surveys were in areas of particular importance to those interested in establishing homesteads on the island, and on assessing the Micronesian megapode and Nightingale reed-warbler populations.

Surveys of forest birds in the northern and southern portions of the island found Micronesian honeyeaters and Micronesian starlings to be abundant. White terns, Collared kingfishers, and the endangered Nightingale reed-warbler were

common in forested zones. White-throated ground-doves were scarce and the endangered Micronesian megapode was rare. Nightingale reed-warblers and megapodes were not detected in open areas. Only the coastal forests and ravine areas supported a diversity of birds and these forests may cover less than one third of the island. Because the majority of the island above 150 m elevation is covered with swordgrass, and few birds use this habitat, total populations numbers are fairly low and birds are densely packed into forested zones. The bird survey transects purposely bisected areas that are being considered for homestead lots. It was found that both the endangered bird species are

concentrated in the proposed homestead site. This is probably because the rest of the island does not have suitable habitat for either of the endangered birds.

Cocos nucifera and Hibiscus tiliaceus were the most abundant tree species.

There is an understory of Aglaia mariannensis in the northern forest and

Psychatria mariana in the south. The presence of the native species is positive as they are wildlife food and habitat. However, there are several species which are important to the wildlife that were not detected. The density of forest tree seedlings is not high enough to maintain the forest over time. The feral animal presence is eliminating the majority of the seedlings, thus, the forest may not regenerate, and erosion of soil may hasten the degradation of existing forest trees by uncovering tree roots. This process has been observed on Anatahan.

Alamagan, is luckily at a crossroads. The destruction of the forest (wildlife habitat) is not as severe as on Pagan or Anatahan. There is still an opportunity to preserve the habitat and wildlife species on the island by eliminating the feral animals. If feral animals are not eradicated, the forest will slowly begin to degenerate, as there will not be a new generation of trees. Older trees will die from effects of erosion and the forests will slowly turn to grasslands. The wildlife populations will decline accordingly.

3

Native forests are confined to ravines on the southern and western slopes.

Introduction

The area around the old village site in the south (Songsong village) and the current homestead site on the northwest side of the island (Patida camp) have vegetation extensively changed by human encroachment. In the south, large stands of breadfruit, lemons and mangos are evident. We encountered feral cattle, pigs, and goats while conducting surveys in every part of the island.

Alvin Fitial (Enforcement), Tina de Cruz and Nathan Johnson (Wildlife)

conducted bird, bat, and vegetation surveys with assistance from Ben, Pat and Ed Santos. Richard Lazaro [Brown Tree Snake (BTS)] and Larry Stoll (Northern Islands) conducted small mammal and lizard surveys. Sylverio Matteo navigated the Northern Islands Mayor's small boat to the southern peninsula.

Transportation to Alamagan from Guguan was provided by Americopters. The survey team left Guguan on 10 June and arrived the same day on Alamagan in time to unload and set up camp. On June 11-16 forest bird surveys, seabird surveys, skink and gecko surveys, rat trapping, and bat counts were conducted.

We climbed the volcanic crater and made camp in the highlands from 14-16 June to observe bats. On June 17, the Marlin II provided transportation of gear and personnel to Saipan.

5

Alamagan south side transect near old village.

Forest Bird Surveys

There have been few previous surveys of Alamagan's forest birds. Play backs were used to elicit responses from the endangered Nightingale reed-warbler (Acrocephalus luscinia, gaga karisu) along a single transect on the south side in 1988 (Reichel et al. 1992). A Variable Circular Plot (VCP) survey of forest birds along one transect on the north side was performed 22-23 May 1990 (Rice et a/.

1990). And a single transect to listen for reed-warblers was conducted in May 1992 (Rice and Stinson) in the northern section.

The number of reed-warblers detected in 1988 was not reported, however, the surveyors estimated the population on the south side (based on territory size and amount of available habitat) to be no less than 100 pairs. The 1990 survey detected 37 reed-warblers along a gradient through ravine forest to 100 m elevation in the northern part of the island (mean per station = 3.08 detections, SO = 1.39). Rice and Stinson (1992) reported them as being common on the northern part of the island, and even from the upper slopes of the volcano in forest patches amid swordgrass. Reichel et a/. (1992) conservatively estimated

an island-wide population of around 350 pairs and thought that there might be as many as 1,000 pairs on island.

The endangered Micronesian megapode (Megapodius laperouse, sasangat) was not detected on the south side of Alamagan in 1988 or on either end of the island in 1990. Finally, 7 individuals were detected on the north side of the island in 1992 (Rice and Stinson 1992) during the Chiba Expedition.

Forest bird surveys were conducted using VCP methodology on 11-13 June 2000. The surveys were conducted in the mornings from 6:00 a.m. to 10:30 a.m.

by teams of two people. One person from each team detected birds both visually and by song for 5 minutes at each station, estimating the distance to each

detection. No playbacks were employed and most birds were counted by their song or call notes. Point counts were performed at "stations" spaced every 150 m along five transects. The transects were set systematically to sample different forest habitats and were composed of between 6 and 14 count stations for a total of 49 stations (Fig. 1).

Transect 1 ran through Hibiscus forest, native forest, and coconut forest mixed with agroforest along the old trail between villages in the north and south. The transect terminated over half way to the southern side. Transect 2 began near the Patik camp, moved through forested habitats and terminated on an exposed area of lava, vines and fallen trees. Transect 3 also began near Patik camp and ascended a ravine toward the betelnut plantation terminating in a sword grass plain. Transect 4 was on the south side and started just as the forest began at the edge of the old village. It ran through Hibiscus and mixed coconut forest, terminating in a ravine rising sharply toward the summit. Transect 5 was in the low lying area of coconut forests on the same southern plain. Point count stations were not permanently marked but can be relocated using the GPS coordinates in Appendix 1.

The most numerous birds in Alamagan forests (Table 1) were Micronesian

honeyeaters (Myzomela rubratra, egigi). The honeyeater was most often seen in open habitats and was evenly distributed in native forest and in forest dominated by coconut trees (Table 2). Micronesian starlings (Aplonis opaca, sali) were also abundant. There were approximately three starlings per station in coconut forests, 2 in native and ravine forests, and 1 in open areas. This difference in distribution was not significant (ANOVA P < 0.2). White terns (Gygis alba), Collared kingfishers (Halcyon chloris, sihek) and Nightingale reed-warblers were all common. The reed-warbler was only found in forested habitats. White­

throated ground-doves (Gallicolumba xanthonura, paluman apaka) were not common, but were detected in all habitats. The endangered Micronesian megapode was rare and only found in native forest.

7

SOIL CONSERVATION SERVICE U.S. DEPARTMENT OF AGRICULTURE

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ALAMAGAN ISLAND

NORTHERN MARIANA ISLANDS 1r 36'06"N x 145⁰ 50' 18"E

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SOURCE: U.S. DEFENSE MAPPING AGENCY

AND SCS FIELD PERSONNEL; PROJECTION I APPROXIMA TE SCALE - MILES

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APPROXIMA TE SCALE - KILOMETERS

MERCATOR GRID. ZONE 55.

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Table 1. Forest birds detected over 5 transects on the northern and southern slopes of Alamagan 11-13 June 2000.

Detections Approximate Bird Species Number per Station numbers expected

Detected (SE) in a 40 ha area

Collared kingfisher 34 0.70 15.8

(0.171)

Micronesian honeyeater 168 3.43 77.9

(0.261 )

Micronesian megapode 2 0.04 0.93

(0.029)

Micronesian starling 133 2.71 61.7

(0.341)

Nightingale reed-warbler 40 0.82 18.6

(0.154)

White tern 38 0.76 17.6

(0.221 )

White-th roated ground-dove 15 0.31 7.0

(0.092)

TOTAL 430 200

The DISTANCE evaluation of the VCP data did not appear practical. Density and population estimates often appeared to be an order of magnitude too high.

More time needs to be spent with this computer program in order to have confidence in the results. In the meantime, it is estimated that bird densities by species in different cover types using fixed radius techniques for each count station (we used a 75 m radius or 1.76 ha). We then extrapolated over the amount of forest cover to estimate an island-wide population (Table 2).

Because the amount of forest cover on Alamagan is low (probably less than one third of the island) estimated population sizes for most species are concomitantly low. However, the population estimate for the Collared kingfisher is surely an underestimate as this is the one bird species that forages broadly over the large expanses of swordgrass using remnant trees as perches. Most other forest birds were concentrated in the coastal and ravine forests as they cannot use the

majority of the island covered with swordgrass.

9

Table 2. Detections of forest birds in different habitat types on Alamagan and estimated population size based on proportions of habitats. Data are truncated at a 75 m radius for these calculations.

Bird Species Habitat

Number per station

Number in 230 ha native forest

Number in 120 ha coconut

forest

Number in 150 ha edge

habitat

Island­

wide Pair Estimate (95% CI) Collared

kingfisher

Native 0.58 75.5

forest

--<j(;cClnut-- '-''''0:4'7''''-' ----'_ ....-.-.-- ..

forest

-''''~dOle-'-' '-'-'''1~O'''-'-- .-.-._.... _....-.­

"'--"'31~-6'-''''- ---.---.---,-, -'-'---'-''''-'--- "'-'-134~7-''''-'

192 (126-258)

Micronesian honeyeater

Native 3.23 419.2

forest

-'<j(;co-nut-' ---3:5'3'-'-' ._.-.---._._ .... - ---'''~39~f5-'-'- ... ---.-.-,--_.-.

forest

-''''~dOle-'-' '---'5:0'0--'-­ ---­ ... -­ ..._­ -'-' ...-.-,...

"''''42'ij'-'-'

1082 (515­

1650) Micronesian

starling

Native 2.45 318.6

forest

-. CO-CClnut-­ ._. --3'.5'3-" .-. .-. -.... ---. -. -.- _. -. -i39-.f5 _... --.

forest

"'-'EdOle-'-' '-'--1:3'3'-'''' .-.-._ ... -.-.­ - -._ ... _.-.-_ ..

-.... -... ­---... _.

-'---11-3:0'-''''

671 (211­

1132) Nightingale

reed-warbler

Native 0.74 forest

---.---­ -_._-_.---.--_.

Coconut 1.13 forest

"'-'EdOle-'''- --'-'-'0''''''''''

96.4

---.-.--- ---.­

76.8

... -._.- .... --­ .. -_.- ... --.-.-._.­

---­

---''''-()''''''''''

173 (120-227)

White-throated ground-dove

Native forest

_.

Coconut forest _._---­

Edge

0.35 0.13 ---­

0.33

46.1

.---.-.---0--­

---­

.

9.0

---­

. . _

----_._--._----.

28.2

83 (68-99)

The two endangered bird species, Nightingale reed-warblers and Micronesian megapodes were only found in forested habitats at lower elevations (Fig. 1).

These forests are among those most highly altered by human intervention, and are also the most highly impacted by feral animals. There were several cows encountered, many goats, and several pigs heard during the survey periods in both the northern and southern sectors. The understory of the forest, however, does not appear to be as denuded as on some other over-grazed islands.

Anecdotally, reed-warblers and megapodes were heard singing and calling in the ravine forests that extend up the flanks of the volcano from the south to at least 350 m above sea level. This information means that megapodes also use the southern portions of the island, although they were not detected during surveys

of the Songsong area. Both chicks and juvenile megapodes were recorded during and after surveys. Reed-warblers were heard during bat surveys in the remnant forests inside the volcanic crater. Reed-warblers or megapodes were not detected in open areas or those covered mainly by sword grass.

The estimate of Nightingale reed-warbler population size, based on these

surveys, is approximately half the size of Reichel et al. 's (1992) estimate from the combined surveys of 1988 and 1990. This makes sense because our detection rate per listening station was also substantially lower than the detection rate in 1990. It may be that the area covered by forest has been underestimated, resulting in an island-wide estimate that is too conservative. It is possible that the more extensive surveys conducted in June 2000 have revealed a less dense or more aggregated population than was previously supposed. It could also be that the population of reed-warblers has declined over the last 10 years under the combined influences of typhoons, habitat loss due to feral ungulates, and

predation pressure. If feral ungulates continue to alter the island's vegetation as they have in the past the island may become subject to desertification almost as severe as that of Anatahan, and the risk of extinction to reed-warblers will be similar to that of the former population on Pagan.

Alamagan homestead site.

II

Only 2 megapodes were detected, both in the northern sector close to the Patik camp, therefore no density estimates were attempted for this small population.

Nightingale reed-warblers were common near the Patik camp in the north (in total, the northern sector had 0.52 reed-warblers per station). They were densely packed in the forests of the southern plateau (the southern sector had 1.44 reed­

warblers per station). The southern area was predominantly mixed forest that was patchy as a result of activities associated with the old village site. We observed several reed-warbler males and females along this sloping plain accompanied by juveniles. Reed-warblers were also observed foraging

throughout the mixed native and coconut forests, often in Hibiscus tiliaceus. This is interesting because it is not a habitat that is frequently used by the population on Saipan. However, the bird's use of a mosaic of forest and open patches is typical of the general pattern also observed on Saipan.

The bird survey transects purposely bisected areas that are being considered for homestead lots. Both of the endangered bird species on the island are

concentrated in these areas so planners might now consider (a) turning their attention to other areas of the island to avoid harassment of the species, or (b) begin designing mitigation measures.

Seabird Surveys

Seabirds were counted as they flew past a fixed point on land near Patik camp on 12 June from 12:00-12:30. We countered 72 Brown noddies (Anous stolidus) , 5 Black noddies (A. minutus) , 2 Brown boobies (Sula leucogaster) and 5 Sooty terns (Sterna fuscata) for a total of 84 birds. Nests of these species were not encounter. It is suspected that seabirds do not nest on exposed parts of the island because of monitor lizards (which were sited) and hunting dogs. There are several small lava islets surrounding Alamagan and it is possible that some seabirds nest on these, or visit from the nearby colonies on Guguan.

Vegetation Surveys

Vegetation surveys were conducted simultaneously with forest bird surveys. Five transects were established, 3 in the northwest near camp and 2 in the south near the village of Songsong. Vegetation was surveyed using a modified point

centered quarter method (Mueller-Dombois and Ellenberg, 1974. Data was taken on trees 2 m in height and greater. Diameter was taken at breast height (DBH) as some trees in the Mariana islands are only buttressed at their bases, usually those under 10cm. Therefore, diameter at the base may lead to

overestimates and misleading interpretations. Canopy coverage was estimated for an area of 5 m² around the station. Ground cover was estimated for 2 m²

around the station. The data were analyzed for ground and canopy coverage, absolute frequency (the number of stations a species is present in / the total number of stations), relative density (the number of individuals of a species/the total number of individuals), and diameter at base height (DBH) size class of species sampled along all transects (Mueller-Dombois and Ellenberg, 1974).

Absolute frequencies and relative densities are expressed as percentages. The data for transects 1, 2 and 3 were pooled for all parameters because these transects are located in the same region, are partially or completely contiguous, and are similar in habitat. Data for transect 4 and 5 were also pooled for the same reasons. Transects 1,2 and 3 will be referred to as the northwest and transect 4 and 5 as the south.

A total of 23 tree species were detected along the five transects. This does not represent all the species on the island. A broad survey such as this is not designed to detect rare species. Cocos nucifera (coconut) and Hibiscus tiliaceous were the most widely distributed of all the species detected. In the northwest transects C. nucifera and H. tiliaceus had the greatest frequency (>50% of the plots). Aglaia mariannensis and Carica papaya were the third most widely distributed species in the northwest (Fig. 2). In the south C. nucifera was found in a 62% of the plots while P. mariana was found in 50% of the plots

followed by H. tiliaceus in 43% of the plots (Fig. 3).

The relative density of Cocos nucifera and H. tiliaceus is greater than all other species on all the transects. In the northern transects Aiglaia mariannensis has the third greatest relative density. In the southern transects C. nucifera and P.

mariana have the greatest relative density followed by H. tiliaceus (Fig. 4).

The DBH size class distribution along the northwest quadrants indicates the predominance of Aglaia mariannensis and H. tiliaceus in seedling and smaller (1­

5cm and 5-10cm ) size classes. Psidum guajava dominates the larger size class (20cm and above) (Fig. 5). Psidum guajava is considered a dangerous invasive species in Hawaii. The overstory in the southern transects were dominated by C.

nucifera (Fig. 6). Psychotria mariana is an important component of the seedling and juvenile tree classes (0-5cm and 5-10cm).

Average canopy cover was 60% or above on transects 1, 3 and 5. The ground cover percent was the least on transect 5 (Fig. 7)

The low abundance and density of most native species present on Alamagan is cause for concern. Species which are heavily utilized by forest birds, bats and coconut crabs such as E. joga, O. mariannensis, F. prolixa, F. tinctoria, P.

tectoria and M. citrofolia appear unusually low whereas the weedy and

introduced species (i.e. C. nucifera, C. papaya, P. gujava and H. tiliaceus) are relatively more abundant and more widely dispersed, especially in the overstory.

It is difficult to predict the health of the forested areas in terms of their long-term ability to continue to propagate themselves with this one picture in time.

13

However, the presence of feral ungulates is cause for concern. On other islands such as Sarigan, Pagan and Anatahan it appears as if the native species are the preferred foraging food. This leaves the weedy and introduced species which are less favored with less competition, allowing them to become dominate.

Alamagan appears to be at a crossroads. It is possible that the feral ungulates have begun to severely decrease the native plant species. If this is the case this trend will continue. One of the interesting aspects of both Alamagan and Agrigan is that the understory, especially the 1-5cm DBH size class is still present. On Pagan and Anatahan it is mostly absent. It may be that the dogs which live on Alamagan and the residents of Agrigan are able to keep the feral population down enough to allow for some seedlings to survive.

List of Vegetation Figures

Figure 2. Absolute frequencies of tree species present on transects 1, 2 and 3 (northwest). Data for transects is pooled (see text for explanation).

Figure 3. Absolute frequencies of tree species present on transects 4 and 5 (southwest). Data for transects if pooled. (see text for explanation)

Figure 4. Relative densities of tree species on transects 1, 2 and 3(northwest) as pooled data and transects 4 and 5 (south) as pooled data (see text for

explanation).

Figure 5. DBH size classes and species distribution within size classes for transects 1, 2, and 3 (northwest). Data is pooled (see text for explanation).

Figure 6. DBH size classes and species distribution within size classes for transects 4 and 5 (south). Data is pooled (see text for explanation).

Figure 7. Average percent canopy and ground coverage for all transects.

Absolute frequency %

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Absolute Frequency for tree species on Transect 4 & 5 (data pooled)

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Relative Density of tree species on Transect 1,2 &3 (data pooled) and Transect 4 _ &5 (data pooled) on Alamagan, June

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Diameter at breast height (DBH) for trees by species on Transect 1, 2 &3 (data pooled) on Alamagan in June 2000

45 ^I

A. altilis

D A. mariannensis

40 - 1 - - - , - - - -

I

Aglaia mariannensis

• C. nucifera

35 -I ­

Citrus sp.

D H. tileaceus .M. indica

30

D N. oppositifolia

P. mariana

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• M. multiglandulosa .P. guajava

o unidentified

30-40cm 40cm+

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Diameter at breast height (DBH) for trees by species on Transect 4 &5 (data pooled) on

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Alamagan in June 2000

A. muricata

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Transect

Herpetological Surveys

The purpose of the surveys on Alamagan were to document the presence and relative abundance of diurnal and nocturnal reptiles.

Diurnal lizards were sampled using adhesive mouse traps (Bauer and Sadlier, 1992; Rodda et aI., 1993). Two transects were sampled, one in mixed coconut forest and one in mixed secondary forest (Fig. 8). Ten traps were placed flush with the ground every 25 meters along each transect. Traps were run for 3 consecutive days. Traps were placed in the morning (0700-0900) and run for 4-6 hours. All lizards captured were taken back to base camp, euthenized,

measured, field-tagged, and preserved. Upon returning to Saipan, all specimen identification was verified and specimens were catalogued and placed in the DFW collection.

Nocturnal lizards were also sampled using adhesive mouse traps. Two transects were sampled, one in mixed coconut forest and one in mixed secondary forest.

Ten traps were set along each transect, spaced every 25 meters, and were stapled to the trunks of trees 0.5-2.0 meters above the ground. Traps were placed 1 hour prior to sunset and checked the following morning. Traps were run for 3 consecutive nights. All lizards captured were taken back to base camp, euthenized, measured, field-tagged, and preserved. Upon returning to Saipan, all specimen identification was verified and specimens were catalogued and placed in the DFW collection.

In an attempt to detect the presence of the snake-eyed skink (Cryptoblepharus poecilopleurus) and the tidepool skink (Emoia atrocostata), 10 adhesive traps were placed for two nights at the beach campsite in rocky strand and grassy habitat.

Tables 3 and 4 show the results of trapping for skinks and geckos. Eight species of lizards were documented. The blue-tailed skink (Emoia

Caeruleocauda) was the most abundant lizard captured (n=112). Also occurring in relatively high numbers were Emoia slevini (n=37) (Fig. 11).

Two new records, and a possible third, were documented for Alamagan: the tide-pool skink (Emoia atrocostata) , and the rock gecko (Nactus pelagicus) (Fig.

9). The tide-pool skink was captured on the rocky-strand beach near the

campsite using an adhesive mouse trap. The Nactus was captured by hand on the ground underneath a dead Cyathea aramaganensis (tree fern) log at 1530h, June 15, at about 1,300 feet elevation. The general habitat of the region was savannah grassland with swordgrass, fern species, tree ferns, club mosses, scattered Pandanus and Elaeocarpus trees.

21

o

I

Fig. 8. Alamagan island showing transects sampled for lizards and small mammals.

Fig 9. The Rock gecko, Nactus pelagicus, was documented for the first time on Alamagan.

23

Table 4. Presence and abundance of lizards trapped on Alamagan, 11 - 15 June, 2000.

Family Gekkonidae

Rocky Beach Savannah

Mixed Coconut Forest

Mixed

Secondary Forest Total

Gehyra muti/ata Gehyra oceanica Lepidodactylus lugubris

Nactus pelagicus 1

3 1 2

2 1 1

5 2 3 1

Family Scincidae

Emoia atrocostata Emoia

caeruleocauda Emoia slevini

1

50 23

62 14

1 112

37

Family Varanidae

Varanus indicus 1 1

Totals 1 1 80 80 162

The mangrove monitor (Varanus indicus) (Fig. 10) was also documented on Alamagan. Biologists reported seeing numerous monitors near the base camp on the island. Also, a specimen was captured near the village (SVL=470,

Mass=1600g). The sex was not documented. This may be the first documented capture of a monitor on Alamagan. Rodda et al. (1991) listed the monitor as a possible resident on Alamagan, but there were no documented sightings or specimens at the time of publication.

The fact that three new lizard records were recorded for Alamagan is more indicative of the relatively few number of herpetological surveys that have been done for the island, rather than a recent introduction of those species. Additional records may be documented and distributional data could be obtained for lizards on the island with additional surveys. Also, Aiamagan, along with Asuncion and Sarigan, is the only northern island with a substantial population of the only endemic skink to the Mariana islands, Emoia slevini, with Alamagan having the densest population (McCoid et ai, 1995) (Fig. 11). McCoid et al (1995) reported

Fig 10. Photo of the Mangrove Monitor, Varanus indicus.

Fig. 11. The only endemic reptile to the Mariana islands, Emoia slevini.

25

a capture rate of approximately 0.033 E. slevini per trap hour for Alamagan. Our capture rate was 0.019 E. slevini per trap hour. This may indicate that the

population is declining, but it may also be due to seasonal fluctuations. Future surveys should investigate the abundance and distribution of this skink on the island.

Small Mammal Surveys

Rats were sampled using Victor rat snap-traps. One transect was sampled in mixed secondary forest (Fig. 8). Twenty-five traps were placed on a tree 0.5-2.0 meters off the ground every 25 meters. Traps were run for 3 consecutive nights.

Traps were set in the evening and baited with peanut butter and left overnight.

Traps were checked the following morning. All rats captured were taken back to base camp, identified to species, and had morphological measurements taken.

The only species of rat captured on Alamagan was Rattus exulans (Table 5).

Rat capture rate was 1.7 rats/100 trap-nights (n=3). Rat populations seem to be relatively low on Alamagan when compared with other islands in the chain. This is good for the native species of wildlife as rats are capable of large amounts of damage to both flora and fauna. Rats were most abundant in mixed coconut forest near the campsite, however, additional trapping needs to be conducted to assess rat abundance on Alamagan as our surveys were not extensive.

Table 5. Results of snap-trapping to assess rat abundance on Alamagan 11­^I 15 June, 2000.

Trap # Rats Rats/100

Habitat Placement Trap Nights* Captured trap nights

Introduced Forest tree 168.0 0 0.0

Mixed Coconut Forest ground 6.0 3 50.0

TOTAL ALAMAGAN 174.0 3 1.7

*Corrected for unavailable traps (Nelson and Clark, 1973).

Mariana Fruit Bat Surveys

Mariana fruit bats (Pteropus mariannus) were counted at 4 stations in two

different locations on Alamagan. The first location was the upper antenna camp

(Fig. 12) where there were 3 separate station counts on two consecutive evenings (June 14 and 15). The second location was the Patida camp were there was 1 station counted on 4 separate evenings (Fig. 12). Station counts were conducted by designating an observation area (Fig. 12) in which the number and flight direction of all bats was recorded. Bats are observed using binoculars or a 60x zoom spotting scope. All station counts began at 16:30 and went until dark (-19:25).

No evident colony or aggregation was discovered on Alamagan. Mariana fruit bats were observed on occasion throughout the trip. Fruit bats were observed flying above and in close proximity to the Patida camp, within the Songsong region (southern village), above the southwestern rim of the main volcanic crater, within the mbin volcanic crater, and above the ocean during the daytime and evening hours. Only four fruit bats were actually seen roosting while on Alamagan.

At station 1 during both the evening station counts the majority of fruit bats were observed flying in and out of the southwestern rim of the crater (Table 6).

Twenty-two individual fruit bats were observed flying within station 2, most of which were observed flying near the main volcanic crater rim and above the forested valley to the south. A total of 12 individual fruit bats were observed flying above the forest within Station 3 (Table 6).

During the station 2 count, fruit bats were observed landing and roosting in Cyathea aramaganensis, Cocos nucifera, and Musa trees (Table 3).

Table 6. M~riana fruit bat evening station count at upper antenna camp on AIamagan, 14 15 J une

-

Date Station Number of Individual Fruit Bats Counted

14 June 1 7

15 June 1 14

15 June 2 22

15 June 3 12

27

73 93 185

~I'~--

&BC 19 May 19 2

239

~5 filM UM

so

ISS R

Ev}~.

.~ ....

~~

II.. lind

46

12

59 ~

23~

(J;rfi.cA- ;

oJ

66 roU.r 191

75

18 12

~o und

65 39 54

16 19 ..nd

12

20 16 ::0-.-,.

17

U-

;1o,V'oL

j ( _cq,~ '~(Gt;..Lc:J

: ( ~ ~'7r,¥(A.q..-L

---4---~q---!---,.----::7c:-6---4---""""'----T---;-:,49---~-­

71 11M ..04

tv

..

iYl.f

f.-deo. ('

<>.""'-f

The Patida station count was conducted from the house at the camp on 5 different nights (Table 7). During this station count bats were observed on several occassins flying on the open ocean. Individual fruit bats were observed flying above the ocean one mile west of Alamagan on two occasions. One of the fruit bats was traveling north, in the direction of Pagan, while the other two were heading south towards the island of Guguan (S. Mettao, pers. comm.).

Table 7. Numbers of fruit bats counted at the Patida camp on Alamagan, 10-13, and 16 June 2000.

Date Number of Individual Fruit Bats Flying Direction

10 June 1 South

11 June 3 2 South 1 North

12 June 13 9 South 4 North

13 June 11 4 South 7 North

16 June 2 North

Mariana fruit bats have been observed traveling between islands by former residents of the northern islands (E. Santos, personal communication) and fishing boat captains (M. Falig, pers. comm.) in previous years. It is likely that the bats are either in search of a more abundant food supply, or as a result of colony disturbances (illegal hunting) are searching for undisturbed roosting sites.

The distances between the Mariana Islands range from 3-65 miles. One other species of Pteropus, P. vampyrus, is known to fly up to 31 miles each night in search of food (Lim 1966). Therefore, Mariana fruit bats are quite capable of traveling the 20 miles to Guguan and the 37 miles to Pagan from Alamagan.

Table 8. Roosting trees and food selection for Mariana fruit bats on Alamagan, June 2000.

Fruit Bat Roosting Trees Fruit Bat Food Selection

Elaeocarpus joga Manqifera indica-fruit

Cyathea aramaganensis Areca spp.- fruit Musa spp.

Cocos nucifera

Fruit bat ejecta were discovered in the Songsong region of Alamagan on the morning of 13 June below a Mangifera indica tree while fruit bat teeth marks were noticed on fresh M. indica fruits. (Table 8). Within this area, a minimum of twenty fruit bats were recorded foraging in M. indica and landing in Cocos trees on the evening of 16 June (B. Santos, personal communication).

29

Mango ejecta.

Other fruit bat feeding sign on Alamagan were noticed on ripe, yellow rinds of Areca fruits (Table 8). Evident teeth marks on the Areca fruits indicated that the fruit bats had been consuming this "reserve food." Areca, Psidium guajava, and Soursop fruits are considered to be "reserve food" for fruit bats on Alamagan (B.

Santos, personal communication). In other words, when the primary food supply is substantially lower than normal (due to typhoons, low amount of rainfall, or habitat degradation), fruit bats may be obligated to select other forms of sustenance.

During their residence on Alamagan, Ben and Eddie Santos (personal

communication) observed fruit bats feeding upon a variety of species (Table 9).

Table 10 lists fruiting and flowering plant species available as food for fruit bats during the June 2000 trip to Alamagan.

Table 9. Observed Mariana fruit bat food items on Alamagan.

Species Structure Manqifera indica Fruit Pandanus tectorius Fruit Arlocarpus altilis Fruit Elaeocarpus joga Fruit Ficus tinctoria Fruit Terminalia catappa Fruit Pouteria obovata Fruit Cocos nucifera Flower Freycinetia reinecki Fruit & Flower Erythrina variegata Flower

Carica papaya Fruit

Soursop Fruit

Psidium guajava Fruit Hibiscus tiliaceus Flower

Areca spp. Fruit

Table 10. Fruiting and flowering plants available as food for Mariana fruit bats on Alamagan 10-17June 2000.

Species Fruiting-S Flowering-F

Manqifera indica S

Pandanus tectorius S

Hibiscus tiliaceus F

Ficus tinctoria S

Melanolepis

multiqlandulosa S

Cocos nucifera S

Aqlaia mariannensis S

Terminalia catappa FS

Aidia cochinchinensis FS

Pouteria obovata S

Psychotria mariana FS

Carica papaya FS

Elaeocarpus ioqa S

Areca spp. S

Jatropha curcas F

Morinda citrifolia FS

, Neisosperma oppositifolia FS

Barrinqtonia asiatica FS

Premna obtusifolia FS

Freycinetia reinecki S

31

Between 19:40-20:24 on 15 June, a minimum of four fruit bats were heard

vocalizing close to the southwestern rim of the crater. It is probable that a colony or small aggregation exists within the crater. In 1992, local residents reported the existence of a fruit bat colony in the crater (Stinson ef al.). On the year 2000 trip, former residents reported that a fruit bat colony was present within the main volcanic crater (E. Santos, personal communication).

Unfortunately, cloudy weather conditions prevented us from obtaining prolonged observations inside the crater. Although, during a small window of visibility, four fruit bats were observed roosting upon the branch of an Elaeocarpus joga tree along the inside of the crater's eastern wall. Present along the crater's eastern wall was a small area of forest containing minimal E. joga, Carica papaya, along with scattered Musa and P. fecforius trees. A majority of the crater was

comprised of Freycinefia reinecki, Miscanthus f1oridulus, and various fern species.

The entire island, including the main volcanic crater, needs to be surveyed in more detail to obtain a definite fruit bat population estimate on Alamagan. On a field trip in 1983, no fruit bats were observed after two consecutive evening counts from the western slope of the main volcanic crater and aboard a ship overlooking Alamagan's west coast ravines (Wiles et al. 1989). In 1992, the main volcanic crater was surveyed for the presence of a fruit bat colony. No bats were observed and it was thought that the habitat inside the crater was not suitable for fruit bat colonies (Stinson et al.).

Based on this trip's observations, Alamagan's fruit bat population appears to be small. However, from all of the individual sightings, evening station count results, and the potential existence of a colony within the main volcanic crater, we

estimate Alamagan to contain a minimum of 200 Mariana fruit bats.

Other Notes of Interest

We did not observe any Coconut crabs (Birgus lafro) on the island. Residents say that the feral pigs have had a large impact on the crab population.

During our 3-day survey of the upper elevations of the island and searches for bat colonies in the volcanic crater we observed several areas of active steam fumaroles. These areas were frequented by feral cattle and we scattered a herd of at least a dozen using a pond below our intended campsite.

Alamagan steam vent.

Cyathea and Freycinetia in upland forest.

We camped for the highland portion of the work on a plateau where the

Emergency Management Office maintains a seismographic device. At the small pond below camp 3 Lesser golden plovers (Pluvialis dominica) were feeding when we first arrived. The area around the pond and down the hillside from the plateau had forest patches interspersed with grassy areas where cows and pigs have caused considerable damage. Forest remnants still contain Cyathea

aramaganensis tree ferns and Freycinetia reinecki, but damage has already been extensive.

Cow and pig damage on Alamagan.

Management Recommendations

• Because the endangered Nightingale reed-warbler and the endangered Micronesian megapode are most abundant in the forests that have been proposed for homestead lots, it would be a good idea for DFW to meet with NIMO and discuss the alternatives in the early phases of the project. It is often best to plan for avoiding some of the birds and to plan potential

mitigation packages for those that cannot be avoided at this early stage than it is later on in the process.

• Intensive studies of Nightingale reed-warbler habitat use, diet, and food availability on Alamagan would assist in preparing to re-establish or translocate populations to other islands.

• A genetic study of the two Nightingale reed-warbler populations should be planned to establish if the two populations have differentiated. This will help guide management decisions concerning a source population for

translocation attempts.

• Long term damage by feral cattle, pigs, and goats to the ecology of Alamagan is evident in all parts of the island we visited. Discussions between DFW and NIMO should begin for working out devices and activities to help improve the situation.

Freycinetia browsed on by feral animals.

Acknowledgments

We are extremely grateful to the Santos family who opened their homestead to us and graciously hosted our stay on Alamagan. Without the help of Ed, Ben, and Pat Santos, and Sylverio Mettao the surveys would have been far poorer and less extensive. Each of these individuals helped get us to different parts of

35

the island and participated in portions of the surveys. A special thanks to Pat who took us to the top of the volcano, through steaming valleys in his bare feet.

Pat stretched out on mountaintop.

There is no way that we can repay Larry Stoll who stepped in for an absent OFW worker and performed lizard, and rat surveys like a professional despite his distaste for reptiles. It was a wonderful experience and we look forward to working together again.

We also thank Mike Cunningham of Americopters for getting us all to Alamagan despite the storm, and Mariano Falig and the crew of the Marlin II for returning us safely.

Literature Cited

Bauer, A.M., and RA. Sadlier. 1992. The use of mouse glue traps to capture lizards. Herpetological Review, 23(4): 112-113.

Lim, B.L. 1986. Abundance and distribution of Malaysian bats in different ecological habitats. Federated Museum Journal 11: 61-76.

Fosberg, F.R, Sachet, M.H., and Oliver, R 1979. A Geographical Checklist of the Micronesian Dicotyledonae. Micronesica 15 (1-2): 41-295.

McCoid, Michael J., G.H. Rodda, and TH. Fritts. 1995. Distribution and abundance of Emoia slivini (Scincidae) in the Mariana islands.

Herpetological Review, 26(2):70-72.

Mueller-Dombois, D. and Ellenberg, H. 1974. Aims and Methods of Vegetation Ecology. John Wiley and Sons Inc., New York. pp100-125.

Nelson, L., Jr. and F.W. Clark. 1973. Correction for sprung traps in catch/effort calculations of trapping results. Journal of Mammalogy, 54(1):295-298.

Reichel, J.D., G.J. Wiles, and P.O. Glass. 1992. Island extinctions: the case of the endangered Nightingale reed-warbler. Wilson Bulletin 104:44-54.

Rice, C.G., and E. Taisacan. 1990. Field trip report, Northern Islands, 18-24 may 1990. CNMI-DFW unpublished report, Pp. 7.

Rice, C.G. and D. W. Stinson. 1992. Field trip report: Chiba Institute Northern islands trip, 11-20 May, 24 May - 9 June. CNMI-DFW unpublished report.

P.p.38.

Rodda, G.H., TH. Fritts, and J.D. Reichel. 1991. The distributional patterns of reptiles and amphibians in the Mariana Islands. Micronesica, 24(2): 195-210.

Rodda, G.H., M.J. McCoid, and TH. Fritts. 1993. Adhesive Trapping II.

Herpetological Review, 24(3): 99-100.

Stinson, D., B. Camacho, F. Dela Cruz, C. Rice, and J. Gourley. 1992. Trip to northern islands with CHIBA Institute. NMI-DFW unpublished report. Pp. 6.

Stone, B. 1970. The flora of Guam. Micronesica 6.

Wiles, Gary J., Thomas O. Lemke, and Nicholas H. Payne. 1989. Population Estimates of Fruit Bats (Pferopus mariannus) in the Mariana Islands.

Conservation Biology 3: 66-76.

37

APPENDIX 1

GPS Coordinates of Forest Bird Transects used for

vep

GPS Coordinates Island Transect Station 55Q UTM

Alamagan 1 1 375000 1947738

Alamagan 1 2 374898 1947596

Alamagan 1 3 374903 1947496

Alamagan 1 4 374864 1947307

Alamagan 1 5 374933 1947220

Alamagan 1 6 374883 1947143

Alamagan 1 7 374803 1947061

Alamagan 1 8 374835 1946948

Alamagan 1 9 374835 1946948

Alamagan 1 10 374835 1946948

Alamagan 1 11 374835 1946948

Alamagan 1 12 374641 1946641

Alamagan 1 13 375069 1946554

Alamagan 1 14 375166 1946498

Alamagan 2 1 375047 1947678

Alamagan 2 2 375175 1947660

Alamagan 2 3 375342 1947687

Alamagan 2 4 375426 1947572

Alamagan 2 5 375542 1947534

Alamagan 2 6 375680 1947540

Alamagan 2 7 375811 1947472

Alamagan 2 8 375957 1947510

Alamagan 2 9 376089 1947585

Alamagan 2 10 376206 1947566

Alamagan 2 11 376289 1947655

Alamagan 2 12 376394 1947747

Alamagan 3 1 375040 1947665

Alamagan 3 2 375112 1947567

Alamagan 3 3 375240 1947491

Alamagan 3 4 375350 1947455

Alamagan 3 5 375422 1947298

Alamagan 3 6 375517 1947192

Alamagan 3 7 375044 1947676

Alamagan 4 1 307553 1944412

Alamagan 4 2 375546 1944413

Alamagan 4 3 375614 1944464

Alamagan 4 4 375747 1944617

Alamagan 4 5 375744 1944617

Alamagan 4 6 375988 1944697

Alamagan 4 7 375988 1944699

Alamagan 4 8 376274 1944628

Alamagan 4 9 376265 1944681

Alamagan 4 10 376647 1944676

GPS Coordinates Island Transect Station 55Q UTM

Alamagan 5 1 375356 1944468

Alamagan 5 2 375415 1944326

Alamagan 5 3 375540 1944320

Alamagan 5 4 375660 1944277

Alamagan 5 5 375795 1944197

Alamagan 5 6 375920 1944240

39